It’s been possible for some time now to auto-hide panels. Now you don’t even need to mess in the configuration files anymore — thanks to a new panel settings menu. Absolutely awesome.
I have to say that I can’t really understand why someone would be unhappy with the way the menu is implemented right now. It’s easily accessable and easy to comprehend (in terms of what it does). If one wants to nit-pick: There’s no way to access the Desktop/Activity properties (wallpaper, Plasma theme etc.) from systemsettings. Boo-boo.